## 20110113

### Astronomy final exam question: Earth vs. moon rock sample ages

Astronomy 210 Final Exam, Fall Semester 2010
Cuesta College, San Luis Obispo, CA

[20 points.] Why do rock samples from the moon's surface have older radioactive dating ages than rock samples from the Earth's ocean bottoms? Explain by discussing properties of planets, and radioactive dating ages.

• p = 20/20:
Correct. Primarily understands renewal versus static nature of Earth's and the moon's surfaces, with at least some discussion of how radioactive dating is "reset" by melting.
• r = 16/20:
Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors. Radioactive dating "reset" discussion is missing or only implied.
• t = 12/20:
Contains right ideas, but discussion is unclear/incomplete or contains major errors. At least recognizes the relative activities of Earth's and the moon's surfaces, but may involve volcanism rather than plate tectonics.
• v = 8/20:
Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. Discussion based on "wear and tear," "exposure," or moon formation theories.
• x = 4/20:
Implementation/application of ideas, but credit given for effort rather than merit.
y = 2/20: Irrelevant discussion/effectively blank.
• y = 2/20:
Irrelevant discussion/effectively blank.
• z = 0/20:
Blank.
Section 70160
p: 7 students
r: 12 students
t: 6 students
v: 10 students
x: 1 student
y: 1 student
z: 1 student

A sample "p" response (from student 1111):

Another sample "p" response (from student 1104):

Yet another sample "p" response (from student 0307):

A sample "v" response (from student 0001), discussing wear and tear on the moon:

A sample "v" response (from student 1919), discussing the fission theory of the formation of the moon:

A sample "v" response (from student 8008), discussing the large impact theory of the formation of the moon: